Many apparatus or machines generate noise and vibrations during operation. In addition, vehicles generate noise and vibrations during operation. Such noise and vibrations can be distracting or annoying to people who use or come into contact with these machines or apparatus. This is particularly problematic with respect to automobiles. In automobiles, asphalt based pads are typically laid on the floorboard to dampen the noise and vibration coming into the passenger compartment. The problem is that floorboards tend to have multiple indentations and shapes, which are difficult to conform to. Often, individual and various shaped asphalt vibration damping pads (usually referred to as “mastic pads”) are manually placed in discreet areas to treat the floorboard area of vehicles. Manual applications of individually shaped parts are an expensive operation in the vehicle assembly process and application and repeatability and reliability is often substandard.
Additionally, the under body of an automobile is subjected to debris during operation. This debris can cause the coating on the underbody substrate to chip.
It is desirable to have a composition that can be applied in such a manner so as to be able to conform to the shape of the substrate. Some patents disclose the use of 100 percent solid content epoxy resin sprayable compositions for this use. For example, see World Patent 99/16840. The compositions disclosed function well, but are quite expensive to use. It is also desirable to provide a composition that aids in chip resistance.
Others disclose latex compositions that are to some degree cross-linked. Crosslinking agents or pre-crosslinked polymers result in relatively good bake characteristics (bake characteristics and bakeability generally refer to the ability to remove water from the composition) but result in relatively poorer vibration damping properties and lower mechanical properties.
Another latex composition is disclosed in U.S. Pat. No. 6,872,761 to LeStarge. This composition includes at least two latexes, one with a glass transition temperature Tg>0 and one with a Tg<0.
Other ways to improve bakeability are also known. These include controlling the material itself, such as by crosslinking the polymer quickly. Another technique has been to pre-crosslink the surface of a film. Finally, lower levels of latex can be used in the formula. Each of these methods results in good bakeability, but a generally lower damping capability.
It is further desirable to provide a near zero volatile organic content (VOC) composition which is conformable to odd shapes and surfaces, can provide good damping properties and can preferably be sprayed or stream applied to the vehicle structure on the sealer application deck. Typically, to achieve the above requirements, materials are required to be solvent borne to reduce viscosity for spray or stream application or are hot melt applied. Application on the sealer deck is required to utilize the benefit of the paint curing ovens, thereby maximizing material conformability and resulting in coalescence or curing to achieve film formation. In general, water containing compositions are not applicable for sealer or paint deck applications because the water vaporizes during the curing process and results in voids, cracking or loss of adhesion to the substrate. To accommodate water-based emulsions in sealer deck applications, one must generally apply low heat for long times to gradually allow water vapor to escape without the formation of voids or cracks due to film formation. It is desirable to provide a composition which is low VOC, water based, can be dried in automobile ovens, can be spray, stream or swirl, etc. applied and which gives excellent damping properties.
Further, current compositions are typically applied to horizontal surfaces in the vehicle such as but not limited to the floor pan. It is desirable to provide a composition that can also be more readily applied to the vertical surfaces such as but not limited to door panels or body panels. It is further desirable to provide a composition that can be cured at room temperature or thermally cured. It is further desirable to have a composition that has higher density, higher solids content, better mechanical properties and better adhesion to metal and painted substrates.